Field of the Invention
The invention relates to the field of extraction appliances for preparing drinks or likewise, from an extraction material contained in a capsule, for example ground coffee (coffee powder). In particular, it relates to a coffee machine.
Description of Related Art
Extraction appliances for preparing drinks or likewise from an extraction material that is present in a portion package amongst other things are known as coffee machines or espresso machines. In many corresponding systems, the portion packages are designed as capsules, in which the extraction material is sealed, for example in an airtight manner. For extraction, the capsule is pierced, for example at two sides that are opposite to one another. An extraction fluid, generally hot water, is introduced at the first side. The extraction product is discharged from the capsule at the second side.
The water must be introduced under a relatively large pressure into the capsule—the pump pressure is often between 15 and 20 bar—for the preparation of various types of coffee, in particular espresso, ristretto or espresso lungo (called cafe crème in Switzerland), and it is only with a sufficiently high brewing pressure that the so-called “crema” so popular amongst coffee enthusiasts can be formed.
On brewing however, with some capsules and indeed with finely ground coffee, it has been found that the flow—thus the volume flow of the fluid flowing into the capsule (and also flowing out of the capsule again, with the exception of a residual quantity remaining in this)—suddenly greatly drops and the user thus obtains an incomplete coffee given a predefined brewing time. This is annoying. Although it would be possible to control the coffee machine such that the brewing procedure continues to be carried out until the defined fluid quantity has flowed through, this however, apart from leading to a greater loading of the pump, also leads to unsatisfactory results concerning the taste.
It would be desirable if an extraction appliance could be designed such that it includes means to ensure that a drink meeting the high quality demands can be brewed from a very high percentage of the used capsules, even given unavoidable fluctuations of capsule characteristics and/or conditions prevailing during the brewing process.